1. Field of the Invention
The present invention relates to an irreversible circuit device and a communication device.
2. Description of the Related Art
Generally, lumped-constant isolators (irreversible circuit devices) employed in mobile communication devices such as portable telephones or the like have a function of allowing a signal to pass only in the transmission direction and blocking the transmission of a signal in the reverse direction. Moreover, for recent mobile communication devices, high reliability and low cost have been more required, due to the type of the uses. Accordingly, for the lumped-constant isolators, higher reliability and lower cost have been strongly required.
The above-described lumped-constant isolators each comprise a permanent magnet, a ferrite to which a DC magnetic field is applied, a plurality of center electrodes arranged on the ferrite, a resin member arranged between the permanent magnet and a capacitor element for matching, an upper case made of a magnetic metal and accommodating the permanent magnet, the ferrite, and the center electrodes, a lower case made of a magnetic metal, and so forth.
FIG. 14 is a vertical cross-sectional view of a part of this isolator in which a resistance element and the matching capacitor element are arranged. In an isolator 200, a matching capacitor element C and a resistance element R are soldered in a lower case 5 formed integrally with a resin case 3. Center electrodes P are arranged on the top faces of the matching capacitor element C and the resistance element R. The matching capacitor element C and the resistance element R are electrically connected to the center electrodes P. A resin member 230 is arranged so as to cover the matching capacitor element C, the resistance element R, and the central electrodes P. The under face of a resin member 230 is formed so as to be flat. Reference numerals 8 and 9 designate an upper case and a permanent magnet, respectively.
In this case, the resin member 230, and the resistance element R and the matching capacitor element C compactly sandwich the central electrodes P. The reasons lie in that the number of the assembling processes is reduced, and a so-called chip-rising phenomenon is prevented when the resistance element R and the matching capacitor element C are soldered.
Referring to the structure of the isolator 200, the resistance element R, the matching capacitor element C, and the center electrodes P are electrically connected to each other on the top faces of the resistance element R and the matching capacitor element C. The resin member 230 locally presses the top faces of the center electrodes P. Accordingly, the pressure used when the isolator 200 is assembled, that is, the permanent magnet 9 is mounted, and the upper case 8 is made to cover, is transmitted to inner components such as the resistance element R and the matching capacitor element C via the resin member 230 and the center electrodes P. Thus, the pressure concentrats onto the parts of the resistance element R and the matching capacitor element C which contact the center electrodes P. In some cases, these inner components are broken. Specially, when the inner components are resistance elements, capacitor elements for matching, or the like made of a ceramic material, problems arise in that these components are ready to be broken.
In the case in which a part (a terminal electrode 211 on the high temperature side of the resistance element R) of the under face of the resistance element R is arranged on the resin case 3, a space e is formed above the terminal electrode 210 on the ground side electrically connected to the lower case 4, corresponding to the thickness of the central electrodes P. Accordingly, when the pressure is applied to the resistance element R, the terminal electrode 211 on the high temperature side of the resistance element R encroaches on the resin of the resin case 3. On the other hand, the terminal electrode 210 on the ground side is lifted from the lower case 4. This causes a problem in that the isolator 200 is unsuitably opened.
Accordingly, it is an object of the present invention to provide an irreversible circuit component of which the structure is easy to be assembled and handled, and the reliability is high.
To achieve the above-described object of the present invention, according to the present invention, there is provided an irreversible circuit component comprising a permanent magnet, a ferrite to which the permanent magnet applies a DC magnetic field, plural center electrodes arranged on the ferrite, an internal component, a resin member arranged between the permanent magnet and the internal component, a metal case accommodating the permanent magnet, the ferrite, the center electrodes, the resin member, and the internal component, the internal component and the center electrodes being electrically connected to each other on the top face of the internal component, the main face near the internal component of the resin member being provided with a step of which the size is substantially equal to the thickness of the center electrodes electrically connected to the internal component.
The internal component is a resistance element, a matching capacitor element, or the like. A part of the under face of the internal component may contact the inner wall of a resin case formed integrally with the metal case. Moreover, the size of the step is preferably in the range of 10 xcexcm to 100 xcexcm. The main face near the internal component of the resin member may be provided with a concavity of which the size is such that the concavity can cover at least a part of the internal component. Furthermore, preferably, the internal component is electrically connected to the center electrodes via solder. Moreover, the distance in the thickness direction of the resin member between the internal component and the resin member is preferably up to 200 xcexcm, and the distance in the thickness direction of the resin member between the center electrodes and the resin member is preferably up to 200 xcexcm.
With the above-described structure, the top face of the internal component can contact not only the center electrodes but also the main face of the resin member, due to the step provided on the main face near the internal component of the resin member. Accordingly, the pressure used when the permanent magnet is mounted, and the metal case is made to cover is divided into the pressure applied to the internal component via the center electrodes and the pressure applied directly to the internal component. As a result, the pressure is dispersed and applied to the whole internal component. Thus, breaking of the internal component is prevented.
Preferably, the resin member is made of one material of a liquid crystal polymer and PPS. The liquid crystal polymer and PPS are superior in high heat resistance and low loss. Thus, the irreversible circuit component having a high reliability can be provided.
The communication device in accordance with the present invention includes the irreversible circuit component having the above-described characteristics. Thus, the communication device of which the cost is low and the reliability is high can be provided.